1. Field of the Invention
The present invention relates generally to the field of oxygen scavenging packaging articles. More particularly, it concerns oxygen scavenging packaging articles wherein oxygen scavenging is initiated by exposure of the packaging article to a peroxide and subsequently an initiating factor, such as heat or ultraviolet light.
2. Description of Related Art
It is well known that limiting the exposure of oxygen-sensitive products to oxygen maintains the quality and extends the shelf-life of the product. For instance, by limiting the oxygen exposure of oxygen sensitive food products in a packaging system, the quality of the food product is maintained, and food spoilage is avoided. Such packaging keeps the product in inventory longer, thereby reducing costs incurred from waste and restocking. In the food packaging industry, several means for limiting oxygen exposure have already been developed, including modified atmosphere packaging (MAP), vacuum packaging and oxygen barrier film packaging.
Another, more recent, means for limiting oxygen exposure involves incorporating an oxygen scavenger into the packaging structure. Incorporation of a scavenger in the package can scavenge oxygen present in the package upon filling with a product. In addition, such incorporation can provide a means of intercepting and scavenging oxygen as it passes through the walls of the package (herein referred to as an “active oxygen barrier”), before the oxygen could reach the packaged product, thus providing even more protection to the packaged product.
In many cases, however, the onset of oxygen scavenging in this system may not occur for days or weeks. The delay before the onset of useful oxygen scavenging is hereinafter referred to as the induction period. Much work has been done to minimize the induction period. Primarily, this work has initiated oxygen scavenging by exposure of the oxygen scavenging packaging article to radiation, especially ultraviolet light (UV) radiation, although other actinic radiation or heat may also be used as an initiating factor.
Typically, the oxygen scavenging packaging article comprises a photoinitiator. Exposure of the packaging article to UV radiation activates the photoinitiator, which presumably depletes any antioxidant present in the packaging article or otherwise allows oxygen to irreversibly react with the oxygen scavenging material.
However, even with the use of a photoinitiator, the induction period is often longer than desired, due to the time required to build up a significant level of free radicals to effectively scavenge oxygen in the package.
Therefore, a need exists for reducing the induction period after triggering by UV, heat, actinic radiation, or another initiating factor or combination of factors.